Chapter 4- Paleoecology- Key Terms

Paleoecology

The study of the life and times of fossil organisms, the lifestyles of individual animals and plants together with their relationships to each other and the surrounding environment.

Actualism

Direct comparisons with living analogs. Also known as uniformitarianism.

Gaia

A concept that describes the planet as a living organism capable of regulating its environment through a careful balance of biological, chemical, and physical processes.

Paleoautecology

The study of the ecology of a single organism.

Paleosynecology

Looks at communities or associations of a single organism.

Time averaging

The mixing of fossil remains from different time periods into a single rock layer or sample.

Fidelity

Similarity of a death assemblage to its living counterpart.

Autochthonous

In place assemblage

Allochthonous

Transported assemblage

Biocoenosis

Living assemblage

Thanatocoenosis

A group of dead organisms or fossils found together in one place.

Taphocoenosis

A group of organism remains or fossils found together in a specific place after undergoing the processes of decay, burial, and fossilization.

Life assemblages

A group of fossils or organisms found together that accurately represents a real, living community from the past.

Neighborhood assemblages

Transported assemblages

A collection of fossils, artifacts, or geological specimens moved by natural agents like water or wind from their original place of deposition to a new location.

Population

A naturally occurring assemblage of plants and animals that live in the same place and same time.

Ecosystem

All the populations living in an association.

Keystone species

Species that help shape the ecosystem.

Incumbent species

An established organism that uses priority effects and local adaptation to block or resist new species from coming into the community.

Survivorship curves

The number of survivors at each defined growth interval is plotted.

Equilibrium species

An organism that thrives in a stable environment by using a competitive survival strategy over quick reproduction.

Opportunistic species

A species that quickly adapts to use new or open spaces and changing surroundings.

Habitat

Where a species lives.

Niche

The role a species fills.

Photic zone

The depth of water penetrated by light.

Nektonic

Free-swimming aquatic animals that move independently of water currents.

Benthos

Creatures that live in or on the seabed.

Infaunal

Aquatic animals that live buried within the bottom sediments, sand, or mud of oceans, lakes, or rivers.

Epifauna

Aquatic animals that live on top of a surface.

Tiering

Marine communities becoming higher and sophisticated through geological time.

Food pyramid

A model showing how energy, biomass, or numbers of organisms decrease as you move up through the feeding levels of an ecosystem.

Food chain

Who eats what.

Guilds

Groups of functionally similar organisms occurring together in a community.

Megaguilds

A range of adaptive strategies based on a combination of life position and feeding type.

Limiting factors

An environmental condition or resource that restricts the growth, abundance, or distribution of an organism or a population in an ecosystem.

Oxygen Minimum Zone (OMZ)

The area of the ocean where the lowest oxygen values are reached.

Isotonic

Same salinity.

Stenohaline

Narrow salinity range.

Euryhaline

Wide salinity range.

Carbonate compensation depth (CCD)

Depth where the rate of calcium carbonate supply from sinking plankton matches its rate of dissolution.

Aragonite compensation depth (ACD)

Ocean depth where the rate of aragonite dissolution equals rate of supply.

Chemotaxic

Responding to chemical signals.

Paleocommunities

Recurrent groups of organisms related to some specific sets of environmental conditions or limiting factors.

Benthic assemblage zones

A community of bottom-dwelling assemblages grouped by their shared presence within a region of the seafloor or aquatic sediment.

Relative abundance

The portion or percentage of one specific item, species, or isotope compared to the total amount in given samples or communities.

Pioneer communities

The first group of organisms that colonize a barren or deserted area.

Equilibrium communities

Stable groups where the number of species and structures remain relatively constant over time.

Eltonian models of change

Predictable over long periods of time

Gleasonian models of change

Short-term, rapid change, instability

Coordinated turnover

Synchronized replacement, recycling, or exchange of components in a system.

Calcretes

Soils rich in calcium carbonate

Evaporites

Evaporated salts

Dropstones

Stones that plummet from the bottoms of melting icebergs into seabed sediments.

Tillites

Rocks and sand left behind by an advancing glacier.